Solid-state drives (SSD) are a form of data storage that uses solid-state memory to store data. Examples of solid state memory include static random access memory (SRAM), dynamic random access memory (DRAM), and flash memory. SSDs are less susceptible to mechanical failures compared to conventional hard disk drives because SSDs do not include as many moving parts as conventional disk drives, which store data on a rotating disk.
Access (i.e., communication) to the SSD may occur through, for example, a Peripheral Component Interconnect Express (PCIe) interface. PCIe is a high-speed serial computer expansion bus standard designed to replace the older Peripheral Component Interconnect (PCI), Peripheral Component Interconnect eXtended (PCI-X), and Accelerated Graphics Port (AGP) bus standards. PCIe SSD (or PCIe SSD accelerator) is a way of adding the speed of a solid-state drive (SSD) to server and storage devices. Additionally, cards in PCIe slots can be changed without shutting down the computer, and they consume less power than previous PCI technology.
An SSD may comprise a plurality of flash memory cells (e.g., NAND or DRAM memory cells). While flash memory has the benefit of being less susceptible to mechanical failures compared to conventional hard disk drives, flash memory also has the limitation of having a finite number of erase-write cycles. Most commercially available flash products are guaranteed to withstand a specific number of cycles before the wear begins to deteriorate the integrity of the storage, for example 100,000 program-erase (P/E) cycles. SSD controllers on PCIe SSD products may track the wear history of the flash memory devices over time so they can notify the host system when a threshold wear limit has been reached. For example, the SSD controllers may notify the host system when a threshold percentage or number (e.g., 5%, 10%, 20%, 30%, etc.) of the finite erase-write cycles remain available on the flash memory devices. This allows the host system to manage when a card or component needs to be replaced and/or warn the user if the flash memory device is getting close to the end of its life.
However, in many PCIe SSD products, the only place to store the wear history of the flash memory devices is in the flash memory devices themselves. Thus, if a flash memory device fails and is replaced, the wear history of the remaining good flash memory devices on that solid state drive could be lost. As most commercially available flash memory products come with a warranty or guarantee to withstand around a specific number cycles, not knowing the wear history causes problems. In the absence of flash memory device wear history records, under estimating or over estimating the remaining life of the flash memory device may short change either the customer or the seller.
Maintaining adequate thermal margins is a key challenge with PCIe SSD products. The flash memory devices (e.g., NAND flash memory devices) located on PCIe SSD products are typically the weakest link from a thermal standpoint. Thus, locating the flash memory devices in such a way as to reduce their temperatures is beneficial in improving the overall thermal margins of the PCIe SSD product.
Yet another challenge associated with PCIe SSD products is maintaining adequate operating power margins. The PCIe standard requires that a PCIe card not draw more than a maximum power limit (e.g., draw more than 25 Watts) from the host socket.
In view of the above, what is needed is a PCIe SSD product that is partitioned into a PCIe card and a separate flash daughter-card.